Mosquito-transmitted parasitic diseases are among the major causes of mortality and morbidity in the world. Recent dramatic increases in the incidence of mosquito-borne diseases, like malaria and dengue fever, and the wide-spread resistance of mosquitoes to insecticides underscores the need for new approaches for insect control based on mosquito-specific agents. The discovery of such mosquito-specific control agents depends on basic research on the biology of mosquitoes. Juvenile hormone (JH) is a major hormonal regulator in insects. In the female mosquito, JH signals the completion of the ecdysis to the adult stage, and initiates reproductive processes. JH titer is essentially determined by the rate at which the corpora allata (CA) synthesizes JH. Our research, using an integrative approach that combines experiments at the organismal, cellular and molecular level, is revealing that mosquito regulation of JH activity has unique features that are related to the adaptation to blood-feeding and the cyclic regulation of ovarian development. We have described that the CA of the female mosquito alternates between periods of high and low biosynthetic activity that are linked to developmental programs and nutritional signals. We have identified neuropeptides that stimulate or inhibit JH synthesis and have characterized their receptors. We have performed the first genomic analysis of an insect endocrine gland and studied the expression of most of the JH biosynthetic enzymes. We have also described that nutrients accumulated during the larval stages regulate CA activity and developed a unique model of nutritionally deficient mosquitoes that do not synthesize JH. The goal of this project is to understand the role and mechanism of action of the different factors that control CA activity (allatoregulatory factors). We also seek to identify the rate limiting steps and regulatory points of JH synthesis. To accomplish these goals, we will focus on two key stages: 1) the activation of JH synthesis in the newly emerged adult female and 2) the inactivation of the CA after blood- feeding. These two stages are critical moments in the reproductive maturation of mosquitoes and make excellent experimental models that are also relevant for disease control. These areas of research should identify targets for designing new, specific and affordable chemical strategies suitable for mosquito control in developing countries.